[TypeSpecValidationAll] Remove PR trigger (#31214)

- TSV should automatically check all specs if "core files" changed
- Was only defense-in-depth
- Was not a required check anyway

eng/pipelines/typespec-validation-all.yml

@@ -5,23 +5,6 @@ trigger:
     - RPSaaSMaster
     - typespec-next
 
-pr:
-  branches:
-    include:
-    - main
-    - RPSaaSMaster
-    - typespec-next
-  paths:
-    include:
-    - .gitattributes
-    - .prettierrc.json
-    - package-lock.json
-    - package.json
-    - tsconfig.json
-    - eng
-    - specification/suppressions.yaml
-    - specification/common-types
-
 resources:
   pipelines:
   - pipeline: typespec